In a disk array device, the state of a hard disk mounted thereon, particularly, the conditions of a head and a medium surface, is checked. Therefore, a disk array device is mounted with the function of checking the state of a hard disk.
As one type of this function of checking the state of a hard disk, there is a function that accesses a given amount of data each time on each disk device in a certain given cycle and performs check on a medium in a disk drive, data consistency check on a RAID (Redundant Arrays of Inexpensive Disks) group, and the like. One type of such cyclical disk checking is provided with a feature called write check (Write Check) and a feature called data check (Data Check). Write check is a feature configured to perform Write, Read, and Compare operations mainly for the purpose of checking a head. Whereas, data check is a feature configured to, mainly for the purpose of checking the medium surface of a disk, run verification on areas used by a user. Here, “verification” means to detect an area in which a fault has occurred and move undamaged data in that area to undamaged areas. For example, a technology called “Data Patrol” exists as a function having these two features that performs cyclical disk check.
Here, there are the following two views about areas on which to run the verification in data check. One view is that only areas having volumes set thereon have to be verified. The other view is that not only areas having volumes set thereon but also unused areas having no volumes set thereon have to be verified. In addition, which one of these two views is adopted for how areas on which to run the verification are determined is an important issue in using a disk array device. The state of use of the disk array device is an important key in thus determining areas on which to run the verification.
In the past, it was often the case that one disk array device was used exclusively by a specific user. For this reason, a prevailing manner of operation was formerly such that volumes were set before shipment and not subject to change after shipment. Therefore, it was formerly possible to presume that areas having volumes set thereon were areas that are appropriate for being subject to data check.
In contrast, a manner of operation such that a large-scale disk array device is used by two or more users at the same time with the internal resources of the device allocated among these users has been becoming increasingly common over recent years. In addition, a manner of operation such that each of the users freely creates and changes volumes has been becoming increasingly common. Therefore, the current situation is such that there is no general rule for determining whether areas appropriate for being subject to data check are only areas having volumes set thereon or areas including unused areas. This is because, although it was formerly possible to presume that unused areas were areas to remain unused in the future, it is recently possible to presume that unused areas are areas that are currently not in use but likely to be used in the future.
With regard thereto, in a case where data check is performed only on areas having volumes set thereon, when a volume is newly created for an unused area, work for creating the volume might be delayed because it is impossible to previously detect abnormality of a medium in this area. On the other hand, always performing data check on areas including unused areas results in performing data check on areas that are unlikely to be used in the near term, which is inefficient.
As a technology for determining areas subject to such data check, there is a related technology that measures the usage rate of a disk or the like, and, when the usage rate of a certain level is reached, performs check on unused areas, and newly uses areas on which check has been already performed (for example, Japanese Laid-open Patent Publication No. 2009-176101). Additionally, there is a related technology that obtains, on the basis of the operating condition of a processor, the state in which a storage device is used, and determines a test capacity of unused areas (for example, Japanese Laid-open Patent Publication No. 04-167046).
However, in the related technology that determines a test capacity of unused areas on the basis of the operating condition of a processor, a processing load for determining unused areas is large and affects the IO (Input Output) performance in the originally intended processing of a disk array device. On the other hand, the related technology that performs check on unused areas on the basis of the usage rate of a disk or the like is not capable of identifying the state in which these unused areas have been immediately before being used, and therefore, is not capable of handling aged deterioration and the like.